Trying to build a pump, but I'm no engineer

Guys, I’m getting frustrated! I’ve posted on other threads recently and have gotten some good responses, but still can’t seem to figure this out. Here’s the deal…I’ve got a Mity-Vac pump and and a gravel cylinder from Petsmart. The tube that comes with the cylinder is about 1/2” in diameter (a rough guess). The tube that comes with the pump (intended to bleed breaks) is a lot smaller; I’m guessing 1/8”.

The first thing I did was take the two different size tubes into a Home Depot and asked a guy in plumbing how I could connect the tubes with different size diameters. I ended up buying 3 small pieces (don’t know correct terms) that do in fact allow for a connection. However, when I tried using the pump I got no pressure.

The next thing I tried doing was eliminating the 1/2” tube and inserting the smaller tube that comes with the pump directly into the cylinder. Now, if any of you have bought a gravel clinder you’ll know that the blue cap at the top of the cylinder has an opening that is designed to fit the 1/2” tube that comes with the product. When you insert the thinner tube there is obviously a gap around it. So, I just used electrical tape and wrapped around the tube where it is inserted into the cylinder in hopes of eliminating the gap where air might leak. Now, the good news is that when I tried pumping I did get a slight vacuum and the pressure rose a little, but as soon as I quit pumping the pressure dropped to zero.

I’ve searched and read almost every thread on this topic. I’ll admit I’m not highly mechanically inclined, but now I just feel dumb? Can someone please help me? Would it help if I posted a picture? Thanks

I think a picture, not drawing, would help. The best situation is a single tube connecting the pump to the cylinder with quick disconnects, but I have never played around with a fish cylinder.

If your hose connections are secure you have to work on a better seal between our body and the cylinder. Have you done any shaving?

Lube the palm of your hand, place the tube tightly on your palm, pump up and then watch and see if the vacuum falls. If it doesn’t, it is a body/tube seal problem. If it does, you have a vacuum leak in your setup someplace.

I noticed that the cap on the top of the gravel cylinder cracked over time due to the pressure. I ended up having to use plastidip over the crack to create a seal again. I too thought it was my pump but it wasnt. Do a test like ThunderSS suggested to see where the leak is coming from.

When I bought my gravel cylinder the tube coming off the cap is roughly 1/2” like you say. There were several connectors with my Mityvac pump that I tried until I found the perfect one to seal it without any problems. Im surprised you had to buy anything else.

I snapped a few pictures of the connector Im talking about. Yours shouldve came with the same thing.

Why not order a tube made specifically for pumping?

When you consider what you are getting, they are not a bad deal. To this day, I do not understand why people will spend 20 bucks on a gravel tube when you can order a real tube for ~$55. Maybe I’m missing something?

First off, thanks for the quick replies. Now the bad news. I did as Thunder suggested and I did not get a seal or a rise in pressure on the palm of my hand. So…this obviously means I have a leak somewhere. I feel certain it is leaking where the tube connects to the cylinder.

After reading what Bigger wrote (and looking at his pics) I went back and took a closer look at the “extra pieces” that come with the Mity-Vac pump. I did find a couple that I thought would solve the problem, but it did not. I know I need to post a picture so everyone can see what I’m talking about. I think I’ve tried every possible connection without success.

I want to just buy a cylinder from LA pumps, but now I’m just determined to figure this out (with y’alls help of course). I’ve never posted a picture so hopefully I can figure out how and post some tomorrow.

Thanks

Are you sure that the pump is capable of making vacuum?

Good point.

Detach everything from the pump except the tubing itself. Put your finger over the other end of the tubing and squeeze the handle to make sure its making vacuum. If the pressure rises and you feel suction against your finger then the problem is else where.

I tried the fish gravel vacume with some success with my mityvac pump. My mityvac pump came with a cone shaped adapter that I could push into the large tube and it sealed well.

I had a leak where the cylinder met with the blue cap. I put electrical tape all the way around it and determined that was where the leak was. I then took off the tape and put a bead of silicone sealant all the way around.

Yes, the pump can create a vacuum. If I put my thumb at the end of the black tube coming directly from the pump one squeeze of the trigger makes the pressure rise to almost 15! I’ve got to figure out how to post a pic so y’all can see.

Then the pump and the black tube are fine. Move on to the next piece and figure out a way to check it for leaks.

Every one of the connections has to be very tight. Wrapping electrical tape around a leak will not seal it. You need better connections. Do what thunder said, you checked the black hose and the pump, it’s OK. Now make the next connection (just one at a time) and test it the same way. If you make a connection, and you get little or no vacuum, then the problem is with that connection. Even with my LA pump and tube I had to use Teflon tape around all the brass screw fitting to get a good air tight seal.

I think your fittings just need to be tighter, just test each connection one at a time. You’ll get it.

Does anyone know where I can find these hose adapters or have any extras? I have looked around my local Home Depot and Ace but haven’t found any.